Catalyst regenerator and a riser terminator used therein

ABSTRACT

A catalyst regenerator for combusting carbonaceous deposits from a catalyst comprising a first chamber which comprises a catalyst inlet for feeding spent catalyst with carbonaceous deposits to the first chamber, a supplemental fuel gas distributor, and a distributor for distributing oxygen containing gas into the first chamber; a riser section extending from the first chamber for transporting the spent catalyst and the flue gas, the riser section comprising an outer wall, at least one slot in the outer wall, and a riser termination device which comprises a substantially internally flat cover plate, at least one arm extending from the cover plate, wherein the arm extends about the slot from the outer wall, the arm comprising an outer shell that encloses the arm and wherein no internal portion of the cover plate extends above an upper surface of the outer shell of the at least one arm is provided.

FIELD OF INVENTION

The disclosure relates to a catalyst regenerator and a riser terminatorused therein.

BACKGROUND OF THE INVENTION

Catalyst regenerators are used in a number of chemical processoperations, including fluid catalytic cracking and catalyticdehydrogenation of lower alkanes. Conventional regenerators typicallyinclude a vessel having a spent catalyst inlet, a catalyst outlet and adistributor for supplying oxygen containing gas to the catalyst bed inthe vessel. Two stage regenerators typically comprise two vessels whichcomplete the oxygen contacting in two distinct steps. In a two stageprocess, the partially spent catalyst along with a gas in which thecatalyst particles are entrained enter the lower vessel and rise througha riser which is capped with a riser terminator. In an outer wall of atop portion of the riser are openings, or slots, which allow the spentcatalyst and product gas to exit the riser. The riser terminatortypically has a cap and a plurality of arms enclosing the slots. The capof conventional riser terminators generally resides a predetermineddistance above the slots, providing internal riser space above the slotsinto which some of the gas and entrained catalyst particles may enterand impinge upon refluxing catalyst and the terminator cap. Suchimpingement with other refluxing particles causes breaking, orattrition, of some of the catalyst particles. After leaving the riserthrough the slots and the arms, the catalyst and gas passes into one ormore cyclone separators. It is desirable to obtain separation of thecatalyst and gas prior to the gas entering the one or more cycloneswhich will, in turn, remove >99% of the catalyst particles from the gas.

SUMMARY OF THE INVENTION

In one embodiment, the disclosure provides a catalyst regenerator forcombusting carbonaceous deposits from a catalyst comprising a firstchamber including a catalyst inlet for feeding spent catalyst withcarbonaceous deposits to said first chamber, an optional supplementalfuel gas, and a gas containing oxygen such as air to a distributor fordistributing said gas into said first chamber to contact said spentcatalyst and combust carbonaceous deposits and the optional supplementalfuel to provide at least a reheated and decoked catalyst that is furtherdeactivated and generate flue gas; a riser section extending from saidfirst chamber for transporting the spent catalyst and the flue gas, theriser section comprising an outer wall, at least one slot in the outerwall, and a riser termination device which comprises a substantiallyinternally flat cover plate, at least one arm extending from the coverplate, wherein the arm extends about the slot from the outer wall, thearm comprising an outer shell that encloses the arm and wherein nointernal portion of the cover plate extends above an upper surface ofthe outer shell of the at least one arm.

In another embodiment, the disclosure provides a riser terminationdevice comprising: (a) substantially internally flat cover plate; and(b) at least one arm extending from the cover plate; wherein no portionof the cover plate extends above any portion of the at least one arm.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view of a first embodiment of the catalystregenerator;

FIG. 2 is an elevational view of a top section of a first embodiment ofa riser showing one embodiment of a riser termination device;

FIG. 3 is a top view of one embodiment of a riser termination device;

FIG. 4 is a top view of a first alternative embodiment of a risertermination device;

FIG. 5 is perspective view of a second alternative embodiment of a risertermination device; and

FIG. 6 is an elevational view of a top section of a first embodiment ofa riser showing one embodiment of a riser termination device showing analternative arm configuration.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, the catalyst regenerator 1 for combustingcarbonaceous deposits from a catalyst is shown. The catalyst regenerator1 includes a first chamber 2 including a catalyst inlet 3 and a secondchamber 5. The catalyst regenerator 1 also includes an oxygen-containinggas distributor 4 and a supplemental fuel distributor, 6. A risersection 10 extends from the first chamber 2. The second chamber 5includes one or more cyclone separators and a reconditioning zone. Asshown in FIG. 1, a primary cyclone 7 and secondary cyclone 8 may bepresent. Reconditioning zone 9 is used to contact the furtherdeactivated catalyst particles with oxygen. The top of riser section 10includes a riser termination device 15. A plurality of grids 11 may bepresent in a lower section of the second chamber 5. The processesconditions for operating a catalyst regenerator for propanedehydrogenation catalyst as shown in FIG. 1 are generally described inUS Patent Application Publication 20140200385, the disclosure of whichis incorporated herein by reference.

The riser section 10 has an outer wall 12, at least one opening 14 inthe topmost section of the outer wall 12. Referring now to FIG. 2, anelevational view of a top portion of the riser section 10 is shown. Theriser section 10 further includes a riser termination device 15 whichcaps the riser section 10. The riser termination device 15 includes asubstantially internally flat cover plate 17.

For each opening 14, the riser termination device 15 includes at leastone arm 19 which extends from the cover plate 15. Each at least one arm19 is formed from an outer shell 31 which has a top portion 31 a and twoside portions 31 b, as seen in FIG. 5. The outer shell 31 forms apartial cover over the opening 14. As shown in FIG. 2, no internalportion of the riser section 10 or cover plate 17 extends above theouter shell 31 of the at least one arm 19, with the proviso that theriser shell 12 may have an upper lip at opening 14 onto which the atleast one arm 19 is attached. Therefore, the catalyst particles in theriser section 10 do not pass internally in the riser above the level ofthe opening 14.

As seen in FIG. 2, external components of the riser section 10 mayextend above the level of the openings 14. Such external components mayinclude a cap 16 which may be attached to the vessel 1 in order tostabilize and/or secure the riser section 10. As further shown in FIG.2, the riser cap 16 may be held in place through one or more straps 18.Straps 18 may be connected to either or both of the vessel 1 and theriser cap 16 in a hinged manner permitting longitudinal and radialexpansion and contraction. As shown in FIG. 2, each strap 18 comprises atubular rod 20 having two open ends into which a metal strip 21 isinserted. Metal strips 21 are preferably sufficiently pliant to allowsome flexion upon thermal expansion and contraction of the riser section10.

In one preferred embodiment, the at least one arm 19 extendstangentially or approximately tangentially from the cover plate, asshown in FIG. 3. In an alternative embodiment, the arm extends radiallyfrom the cover plate as shown in FIG. 4. To further describe the anglethat the arm may extend from the cover plate, each of FIGS. 3 and 4further denote point A as a centerpoint of between the two sides 31 b ofthe arm 19. From point A, a dotted line is drawn wherein the dotted lineis parallel to the two sides 31 b of the arm 19. Where the dotted lineintersect the outside edge of the cover plate 17 is point B. A dashedline is drawn tangential to cover plate 17 and passing through point B.The angle D between the dashed and dotted lines as shown in FIGS. 3 and4 may range from 90° (as in the case of the arm extending radially) to0°. All individual values and subranges from 0 to 90° are included anddisclosed herein; for example, angle D can range from a lower limit of),greater than 0, 10, 20, 30, 40, 50, 60, 70, or 80 degrees to an upperlimit of 10, 25, 35, 45, 55, 65, 75, 85 or 90 degrees. As used herein,angle D is defined as the “arm angle”. The arm angle may be from 0 to90°, or in the alternative, from 10 to 65°, or in the alternative, from45 to 90°, or in the alternative, from 20 to 65°, or in the alternative,from 1 to 90°.

The at least one arm 19 may extend substantially horizontally outwardfrom the cover plate 17 for a distance, as shown in FIG. 2 beforeturning downward. Alternatively, the at least one arm 19 may turndownward proximate to the cover plate 17 as shown in FIG. 5.

FIG. 6 illustrates an alternative arm configuration wherein the armincludes an arm extension 32 which extends vertically below the sidesections 3 lb of outer shell 31. FIG. 5 similarly shows such alternativearm configuration. The arm extension 32 may be in the shape of a squaredor rounded U. FIG. 6 further illustrates stiffening ribs 35 used toprovide mechanical strength to the riser cap 16. In an alternativeembodiment, the arm extension 32 extends below a lower edge of opening14.

In one embodiment, the aspect ratio (height divided by width) of the atleast one slot ranges from 1.0 to 4.0. All individual values andsubranges from 1.0 to 4.0 are included and disclosed herein; forexample, the aspect ratio of the at least one slot may range from alower limit of 1.0, 2.0, or 3.0 to an upper limit of 1.5, 2.5, 3.5 or4.0 For example, the aspect ratio of the at least one slot may rangefrom 1.0 to 4.0, or in the alternative, from 2.0 to 3.5, or in thealternative, from 1.0 to 2.5, or in the alternative, from 2.5 to 4.0.

The disclosure provides the catalyst regenerator and riser terminationdevice according to any embodiment disclosed herein, except that theriser flux is from 1 to 200 lb/ft² sec. All individual values andsubranges from 1 to 200 lb/ft² sec are included and disclosed herein;for example, the riser flux may range from a lower limit of 1, 25, 75,120, 169, or 180 lb/ft² sec to an upper limit of 10, 50, 100, 150, or200 lb/ft². For example, the riser flux may be from 1 to 200 lb/ft² sec,or in the alternative, from 1 to 100 lb/ft² sec, or in the alternative,from 100 to 200 lb/ft² sec, or in the alternative, from 5 to 100 lb/ft²sec, or in the alternative, from 1 to 50 lb/ft² sec.

The disclosure provides the catalyst regenerator and riser terminationdevice according to any embodiment disclosed herein, except that thesuperficial velocity of the riser varies from 10 to 70 ft/s. Allindividual values and subranges from 10 to 70 ft/s are included anddisclosed herein; for example, the superficial velocity of the riser canrange from a lower limit of 10, 20, 30, 40, 50, or 60 ft/sec to an upperlimit of 15, 25, 35, 45, 55, 65, or 70 ft/sec. For example, thesuperficial velocity of the riser may be from 10 to 70 ft/sec, or in thealternative, from 10 to 40 ft/sec, or in the alternative, from 40 to 70ft/sec, or in the alternative, from 20 to 50 ft/sec.

In a particular embodiment, the velocity of the stream exiting the armsis determined by X*(A_(riser)/A_(openings)) wherein X is the velocity ofthe stream in the riser and (A_(riser)/A_(openings)) is the ratio of thecross section area of the riser (A_(riser)) to the sum of thecross-sectional areas of the openings 14 which communicate with the arms19 and which are located at the top of the riser (A_(openings)). In oneembodiment, A_(riser)/A_(openings) is from 0.1 to 4.0. All individualvalues and subranges from 0.1 to 4.0 are included and disclosed herein;for example, X may range from a lower limit of 1.25, 1.35, 1.45, 1.55,1.65, 1.75, or 1.85 to an upper limit of 1.3, 1.4, 1.5, 1.6, 1.7, 1.8,1.9, or 2. For example, X may range from 1.25 to 2, or in thealternative, from 1.25 to 1.65, or in the alternative, from 1.55 to 2.

EXAMPLES

Using the BARRACUDA VIRTUAL REACTOR modeling software, which iscommercially available for licensing from CPFD Software, LLC(Albuquerque, N. Mex.), the ability to separate catalyst particles fromthe gas in which it is entrained was modeled. In the ComparativeExample, the riser termination device shown in FIG. 2 of U.S. Pat. No.7,799,287 with four arms was modeled. The Comparative Example wasmodeled with the following parameters: total of the 4 riser opening areaof 5256.6 in²; and riser inlet area of 2375.8 in². In the InventiveExample, a riser termination device according to the present disclosure,having four arms extending tangentially from an internally flat coverplate, was modeled. The Inventive Example was modeled with a riseropening aspect ratio of 2.7; total of the 4 riser opening area of 5205.6in²; and riser inlet area of 2375.8 in². The conditions for both of theexamples were as follows: riser diameter=55 inches; gas velocity throughriser=35 ft/s; solids flow rate through riser=164.14 kg/s=1,300,000lb/hr; and solids flux=21.89 lb/ft²s. The Comparative Example modelpredicted separation of 88.4% of the entrained catalyst particles. TheInventive Example model predicted separation of 94.3% of the entrainedcatalyst particles.

The present invention may be embodied in other forms without departingfrom the spirit and the essential attributes thereof, and, accordingly,reference should be made to the appended claims, rather than to theforegoing specification, as indicating the scope of the invention.

We claim:
 1. A catalyst regenerator for combusting carbonaceous depositsfrom a catalyst comprising: a first chamber which comprises a catalystinlet for feeding spent catalyst with carbonaceous deposits to saidfirst chamber, a supplemental fuel gas distributor, and a distributorfor an oxygen containing gas for distributing oxygen containing gas intosaid first chamber to contact said spent catalyst and combustcarbonaceous deposits and supplemental fuel which further deactivatesthe spent catalyst and generates flue gas; a riser section extendingfrom said first chamber for transporting the spent catalyst and the fluegas, the riser section comprising an outer wall, at least one slot inthe outer wall, and a riser termination device which comprises asubstantially internally flat cover plate, at least one arm extendingfrom the cover plate, wherein the arm extends about the slot from theouter wall, the arm comprising an outer shell that encloses the arm andwherein no internal portion of the cover plate extends above an uppersurface of the outer shell of the at least one arm.
 2. The catalystregenerator according to claim 1, wherein the outer shell of the arm hasa horizontal section extending outward for a predetermined distance fromthe cover plate.
 3. The catalyst regenerator according to claim 1,wherein the arm further comprises an arm extension extending below alower edge of the arm.
 4. The catalyst regenerator according to claim 1,wherein a lower arm section has a vertical U-shape.
 5. The catalystregenerator according to claim 1, further comprising a second chambercontaining the arm or arms, the second chamber comprising a cycloneseparator for separating the catalyst from the oxygen containing gas, aregenerated catalyst outlet and a flue gas outlet.
 6. The catalystregenerator according to claim 1, wherein A_(riser)/A_(openings) is atleast 0.1.
 7. The catalyst regenerator according to claim 1, whereinA_(riser)/A_(openings) is from 0.1 to 4.0.
 8. The catalyst regeneratorvessel according to claim 1, wherein the at least one arm turns downwardproximately to the cover plate.
 9. The catalyst regenerator according toclaim 1, wherein an aspect ratio (height divided by width) of the slotis from 1.0 to 4.0.
 10. The catalyst regenerator according to claim 1,wherein a riser flux is from 1 to 200 lb/ft²-sec.
 11. The catalystregenerator according to claim 1, wherein a superficial velocity of theriser is from 10 to 70 ft/s.
 12. The catalyst regenerator according toclaim 1, wherein a velocity of a stream exiting the at least one arms isdetermined according to X*(A_(riser)/A_(openings)).
 13. A risertermination device comprising: (a) a substantially internally flat coverplate; (b) at least one arm extending from the cover plate; wherein thearm comprises an outer shell that encloses the arm and wherein nointernal portion of the cover plate extends above an upper surface ofthe outer shell of the at least one arm.
 14. The riser terminationdevice according to claim 13, wherein the at least one arm extendstangentially from the cover plate.
 15. The riser termination deviceaccording to claim 13, wherein the at least one arm extends radiallyfrom the cover plate.
 16. The riser termination device according toclaim 13, wherein the arm angle is from 0 to 90 degrees.